Inks and other compositions incorporating limited quantities of solvent advantageously used in ink jetting applications

ABSTRACT

Radiation curable inks with moderate amounts of solvent with low surface tension provide unique processability characteristics that allow ink jetted features to be formed and cured with excellent flow, adhesion, dot gain, compatibility, weatherability, and curing characteristics. In a representative printing method, an ink jettable ink composition is provided that includes one or more oligo/resins, a radiation curable, reactive diluent having a surface tension and 1 to 15 weight percent of a solvent component comprising a solvent having a surface tension. The solvent surface tension is no more than about, and preferably at least 2 dynes/cm less than, the surface tension of the reactive diluent. The ink composition is ink jetted onto the substrate to form an ink jetted feature. While at least a portion of the solvent is still present in the ink jetted feature, the ink jetted feature is exposed to an amount of curing energy under conditions effective to at least substantially cure the radiation curable component of the printed feature and to at least substantially dry the ink jetted feature.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.09/711,345, filed Nov. 9, 2000, now U.S. Pat. No. 6,558,753, thedisclosure of which is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to low viscosity, ink jettable, radiationcurable compositions incorporating limited quantities of solvent toprovide the compositions with viscosity, wettability, compatibility, andrapid curing advantages. The compositions generally include a radiationcurable component (containing one or more radiation curable monomers,macromers, oligomers, and/or polymers), a solvent, and optionaladditives such as colorants, photoinitiators, and the like. Thecompositions are particularly well-suited for forming ink jetted,radiation cured printed features on substrates such as signs, walkways,roadways, motor vehicles, boats, aircraft, furniture, equipment, and thelike. The compositions are particularly well-suited for use in outdoorapplications.

BACKGROUND OF THE INVENTION

Inkjet imaging techniques have become very popular in commercial andconsumer applications. Ink jet printers operate by ejecting ink onto areceiving substrate in controlled patterns of closely spaced inkdroplets. By selectively regulating the pattern of ink droplets, ink jetprinters can produce a wide variety of printed features, including text,graphics, images, holograms, and the like. Moreover, ink jet printersare capable of forming printed features on a wide variety of substrates,as well as three-dimensional objects in applications such as rapidprototyping.

Thermal ink jet printers and piezo inkjet printers are the two maintypes of ink jet systems in widespread use today. For both approaches,inks must meet stringent performance requirements in order for the inksto be appropriately jettable and for the resultant printed features tohave the desired mechanical, chemical, visual, and durabilitycharacteristics. In particular, inks must have relatively low viscositywhen jetted, yet must be able to form accurate, durable images on thedesired receiving substrate. For example, a typical ink for thermal inkjetting must typically have a viscosity in the range of 3 to 5centipoise at 25° C., while piezo inks must typically have a viscosityin the range of 3 to 30 centipoise at the jetting temperature. The needto use low viscosity inks makes it challenging to obtain printedfeatures with good mechanical, chemical, visual, and durabilitycharacteristics.

Solvent-based and water-based jettable inks are well known. A typicalwater-based ink generally comprises water, a colorant, which may be adye and/or a pigment, one or more co-solvents, and one or more additivesthat are included to enhance the performance of the ink. Representativeexamples of such additives include one or more colorants, slipmodifiers, thixotropic agents, foaming agents, antifoaming agents, flowor other rheology control agents, waxes, oils, plasticizers, binders,antioxidants, fungicides, bactericides, organic and/or inorganic fillerparticles, leveling agents, opacifiers, antistatic agents, dispersants,and the like.

Water-based inks have drawbacks. For industrial applications, drying isenergy and equipment intensive. Drying water also takes time, and theprinted material needs to be handled carefully during the relativelylengthy drying period. Water-based inks are also compatible only with alimited range of substrates, typically those on which the water isabsorbed to some degree. Images formed using water-based inks typicallyrequire a protective overlaminate for outdoor applications.

Instead of water, other solvent-based inks include relatively volatile,inorganic solvents. Such inks dry more rapidly and easily than aqueousinks. However, such solvents may be toxic, flammable, or the like,requiring careful handling. These inks also tend to be compatible withonly a limited range of substrates.

In order to avoid using a conventional solvent, ink compositionsincorporating a free radically polymerizable diluent have beendeveloped. The diluent not only functions as a solvent, but alsofunctions as a viscosity reducer, as a binder when cured, and optionallyas a crosslinking agent. In the uncured state, these compositions have alow viscosity and are readily jetted. However, the polymerizablemonomers readily crosslink upon exposure to a suitable source of curingenergy, e.g., ultraviolet light, electron beam energy, and/or the like,to form a crosslinked polymer network. Depending upon the kind ofmonomers incorporated into the diluent, the resultant network mayprovide the printed features with durability, flexibility, elasticity,gloss, hardness, chemical resistance, stiffness, combinations of these,and the like.

There are many instances in which relatively large amounts of solventhave been incorporated into radiation curable ink compositions. Forexample, EP 407,054 (1990) and U.S. Pat. No. 4,978,969 each describeradiation curable ink jet inks containing 10 to 40 weight percent ofsolvent. JP 9-314981 (1997) describes ink jet inks containing greaterthan 40 weight percent of methyl ethyl ketone (MEK) solvent. U.S. Pat.No. 5,623,001 describes radiation curable ink jet inks containing 20 to75 weight percent water. The use of ink compositions containingrelatively large amounts of solvent that might require separate dryingsteps is desirably avoided.

There are other instances in which relatively little if any solvent hasbeen incorporated into radiation curable ink compositions. For example,EP 540,203 (1993) and U.S. Pat. No. 5,275,646 describe radiation curablecompositions with no solvent. JP 9-183929 (1997) and WO 98/27171 alsodescribe solvent-free compositions. WO 99/29787 and 99/29788 bothdescribe radiation curable ink jet inks containing less than 1% solvent.

WO 97/31071 (corresponding to U.S. Pat. No. 6,114,406) also describesink jet inks with limited solvent content. The document genericallysuggests that the inks may contain up to about 10 weight percentsolvent, but the examples only describe ink formulations that do notinclude any solvent. The compositions also must include major amounts ofalkoxylated or polyalkoxylated material, but unfortunately suchcompositions tend to have poor weatherability, adhesion, andcompatibility characteristics due to the high alkoxylated content in themain chain(s) of the resultant cured matrix.

Substrate compatibility is an important characteristic of radiationcurable compositions, particularly for industrial or signageapplications in which printed features may be formed upon a wide varietyof different substrate materials. However, many radiation curablecompositions show good wettability and adhesion to only a limited rangeof substrates, requiring maintenance of several different kinds of inksin those environments in which a wide variety of substrates are likelyto be encountered. Many radiation curable ink compositions, particularlythose incorporating significant quantities of main-chain alkoxylated orpolyalkoxylated functionality, also suffer from poor weatherability inoutdoor applications. It would be desirable to provide ink jet inks thatare compatible with a wide range of different porous and nonporoussubstrates.

Rapid curing of radiation curable compositions is highly desirable toincrease production capacity and throughput. However, oxygen in theambient can have a tendency to inhibit free radical polymerizationreactions. While oxygen inhibition can be avoided by curing materials inan inert atmosphere, maintaining an inert atmosphere during cureinvolves extra equipment and expense. Curing in an inert atmosphere alsomay not be practical in some applications. Accordingly, it would behighly desirable to provide ink jet inks that cure rapidly in theambient and for which the risk of oxygen inhibition in the ambient issignificantly reduced. It would be even more desirable if such curingcould be carried out without resort to an inert atmosphere.

Ink jet compositions also require good dot gain characteristics. Dotgain refers to the degree to which an ink jetted drop spreads out uponapplication to a substrate. If an ink jetted drop spreads out too muchon the substrate, then poor edge definition and intercolor bleed isobserved. On the other hand, if an ink jetted drop spreadsinsufficiently upon application to the substrate, then poor colordensity is likely to result. Dot gain characteristics depend uponfactors including the nature of the ink jet composition, substratetemperature, interfacial tension between the ink and the substrate, andthe nature of the substrate. Some inks show favorable dot gaincharacteristics on some substrates, but not on others. It would bedesirable to provide ink compositions that have consistently good dotgain characteristics with a wide variety of different porous andnonporous substrates.

Typically, to improve wetting and dot gain, the surface tension of anink is lowered by adding flow agents. Flow agents are present atrelatively low concentrations. A typical ink formulation, for example,includes up to 0.1 to about 1 weight percent of one or more flow agents.Commonly used flow agents are either silicone or fluorine based. Bothclasses of flow agents have drawbacks. Silicone based flow agents mayhave a tendency to reduce adhesion of the ink to the substrate. Fluorinebased flow agents are becoming subject to increasingly stringentenvironmental regulations and restrictions. Even when added in suchsmall amounts, flow agents in general may cause too large a decrease insurface tension, resulting in meniscus instability at the ink jetnozzle. Meniscus instability can cause poor ink reliability, flooding ofthe nozzle plate, and raises the need for frequent priming of theprinthead. Therefore, although appropriate surface tension propertiesare required for good printing performance, it would be desirable toachieve such properties without including flow agents in inkformulations.

SUMMARY OF THE INVENTION

The present invention is based, in part, upon the discovery thatradiation curable inks with moderate amounts of a low surface tension(and preferably volatile) solvent component provide uniqueprocessability characteristics that allow ink jetted features to beformed and cured with excellent flow, adhesion, dot gain, compatibility,weatherability, and curing characteristics. The presence of some solventin the compositions promotes wettability and compatibility with manydifferent substrate materials. Indeed, in preferred embodiments,selecting a solvent that penetrates into the substrate helps promoteinteraction, and hence adhesion, between the substrate and the ink. Theuse of some solvent also results in a dramatic decrease in compositionviscosity. This expands the range and content of monomers, macromers,oligomers, and/or polymers that can be incorporated into inks whilestill retaining ink jettable viscosity characteristics. By selectingsolvents with low surface tension, the overall surface tension of theink is reduced, eliminating the need for separate flow agents. Ineffect, the solvent with low surface tension properties performs adouble function as both solvent and flow agent.

Yet, by using a limited amount of solvent, the solvent is easily removedto provide dry, ink jetted features. In preferred embodiments, the inkjetted features can be dried using only the heat generated duringradiation curing so that at least major portions of drying and curingcan occur substantially in the same step. In short, wet, ink jettedfeatures can be radiation cured and dried at the same time.

Faster radiation curing also occurs when the inks include a moderateamount of solvent. While not wishing to be bound by theory, the fasterradiation cure rate is believe to be due, at least in part, to thepresence of the evaporating solvent. The solvent vapors generated by theheat of curing are believed to form a barrier over the printed features.This barrier prevents ambient oxygen from easily reaching the surface ofthe curing features, where the oxygen might otherwise inhibit freeradical polymerization. In practical effect, a protective barrieradvantageously is generated over the features in situ as the cureoccurs. Due to the enhancement of the cure rate and the elimination of aneed for a separate drying step, production speeds of over 1000 ft²/hrcan be achieved when using inks of the present invention.

Additionally, reducing or preventing oxygen inhibition of the freeradically cured ink produces images with cured surfaces that cure betterand are tack free if desired.

In one aspect, the present invention relates to a method of making anink jettable fluid composition. According to the method, a solventcomponent to incorporate into the composition is selected, wherein thesolvent component comprises a solvent having a surface tension andwherein the solvent is selected for incorporation into the compositionfrom information comprising a solvent characteristic indicative of thesolvent surface tension. Once selected, from about 1 to about 15 weightpercent of the solvent is incorporated into a composition comprisingsaid solvent and a radiation curable, reactive diluent having a surfacetension, wherein the surface tension of the solvent is no more thanabout, and preferably at least about 2 dynes/cm less than, the surfacetension of the radiation curable reactive diluent. The composition alsocomprised one or more oligo/resins. Thereby, the ink jettable fluidcomposition is formed.

In another aspect, the present invention relates to a method ofprinting. An ink jettable ink composition is provided that includes oneor more oligo/resins, a radiation curable, reactive diluent having asurface tension, and 1 to 15 weight percent of a solvent componentcomprising a solvent having a surface tension. The solvent surfacetension is no more than about, and preferably at least about 2 dynes/cmless than, the surface tension of the reactive diluent. The inkcomposition is jetted onto the substrate to form an ink jetted feature.While at least a portion of the solvent is still present in the inkjetted feature, the ink jetted feature is exposed to an amount of curingenergy under conditions effective to at least substantially cure theradiation curable component of the printed feature and to at leastsubstantially dry the ink jetted feature.

In another aspect, the present invention relates to a jettable inkcomposition. The composition includes one or more oligo/resins, aradiation curable component comprising a radiation curable, reactivediluent having a surface tension; from about 1 to about 15 weightpercent of a solvent having a surface tension, wherein the solventsurface tension is no more than about, and preferably at least about 2dynes/cm less than, the surface tension of the reactive diluent surfacetension; and an amount of a colorant effective to provide the ink whencured with a visually discernable optical characteristic.

In another aspect, the present invention relates to a jettable inkcomposition, comprising one or more oligo/resins; a radiation curablecomponent; about 0.5 to about 20 weight percent of an ester solventcomprising a branched aliphatic moiety, said ester solvent having asurface tension less than about 30 dynes/cm; and an amount of a coloranteffective to provide the ink when cured with a visually discernableoptical characteristic.

In another aspect, the present invention relates to a jettablecomposition, comprising one or more oligo/resins; a radiation curablecomponent comprising no more than about 30 weight percent of alkoxylatedor polyalkoxylated ingredients; about 0.5 to about 15 weight percent ofa solvent having a surface tension of less than 30 dynes/cm; and anamount of a colorant effective to provide the ink with a visuallydiscernable optical characteristic.

In another aspect, the present invention relates to a jettable inkcomposition comprising a solvent having a surface tension of less thanabout 30 dynes/cm and a flash point of at least 50° C., said compositionbeing at least substantially free of flow control agents comprisingfluorinated and/or silicone moieties.

Preferred embodiments of one or more aspects of the present inventionmay include one or more of several desirable features of which thefollowing list is representative:

the surface tension of the solvent is less than about 30 dynes/cm;

the solvent is nonpolar;

the composition is at least substantially free of flow control agentscomprising silicone and/or fluorinated moieties;

the solvent is an acetate ester;

the composition is substantially nonconductive;

the solvent has a flash point of at least 50° C.;

the composition comprises 1 to 10 weight percent of the solvent;

the solvent is an ester comprising a branched aliphatic moiety including4 to 20 carbon atoms;

the branched aliphatic moiety is a branched alkyl moiety, e.g., anisoalkyl moiety; and/or

the solvent is at least substantially free of radiation-curablemoieties.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather the embodimentsare chosen and described so that others skilled in the art mayappreciate and understand the principles and practices of the presentinvention.

Durable, weather resistant, features such as text, bar codes, graphics,images and/or other indicia may be formed on one or more receivingsubstrates in one or more desired patterns by applying and then curingfluid composition(s) of the present invention. Preferred embodiments ofthe present invention are in the form of colored inks or protectiveclearcoat inks.

Prior to curing, fluid compositions of the present invention preferablyhave one or more of several desirable features. Firstly, radiationcurable compositions of the present invention tend to have sufficientlylow viscosity properties so that the fluid compositions advantageouslymay be applied to receiving substrates using ink jetting techniques.Preferably, fluid compositions of the present invention have a viscosityof below about 30 centipoise, preferably below about 25 centipoise, andmore preferably below about 20 centipoise at the desired ink jettingtemperature (typically from ambient temperature up to about 65° C.).However, the optimum viscosity characteristics for a particularcomposition will depend upon the jetting temperature and the type of inkjet system that will be used to apply the composition onto thesubstrate. For example, for piezo ink jet applications, a typicaldesired viscosity is about 3 to about 30 centipoise at the print headtemperature. Generally, this means that the fluid compositionspreferably have a viscosity at 25° C. of up to about 50 centipoise.Particularly preferred embodiments of the fluid compositions describedherein tend to have viscosities in the range of 10 to 16 centipoise atmoderate temperatures of 25° C. to about 65° C.

Such viscosity characteristics generally help to ensure that thecomposition will be jettable at the desired print head temperature. Dueto potential volatility and reactivity of one or more constituents ofradiation curable compositions, the fluid compositions preferably arejetted at temperatures no higher than about 65° C., and more preferablyno higher than about 50° C.

As another preferred characteristic that is desirable for ink jettingapplications, fluid compositions of the present invention desirably havemoderate to low surface tension properties. Preferred formulations havea surface tension in the range of from about 20 dynes/cm to about 50dynes/cm, more preferably in the range of from about 22 dynes/cm toabout 40 dynes/cm at the printhead operating temperature. Most radiationcurable, monomeric constituents (hereinafter referred to as the“reactive diluent”) to be incorporated into the radiation curablecomponent of the present invention, as well as the preferred solventsdiscussed below, already have surface tension characteristics in thepreferred ranges. Therefore, formulating fluid compositions of thepresent invention with appropriate surface tension characteristics forink jet applications is easily accomplished.

Preferred fluid compositions of the present invention also haveNewtonian or substantially Newtonian viscosity properties. A Newtonianfluid has a viscosity that is at least substantially independent ofshear rate. As used herein, the viscosity of a fluid will be deemed tobe substantially independent of shear rate, and hence at leastsubstantially Newtonian, if the fluid has a power law index of 0.95 orgreater. The power law index of a fluid is given by the expression

η=mγ^(n-1)

wherein η is the shear viscosity, γ is the shear rate in s⁻¹ m is aconstant, and n is the power law index. The principles of the power lawindex are further described in C. W. Macosko, “Rheology: Principles,Measurements, and Applications”, ISBN #1-56081-579-5, page 85.

Newtonian or substantially Newtonian fluid compositions are especiallypreferred over non-Newtonian fluids that exhibit substantial shearthinning behavior. Typically, substantially shear thinning fluids areelastic. Elasticity of a fluid tends to cause extension thickeningbehavior, which is known to prevent jetting of inks even when the lowviscosity requirement is satisfied. Another reason for using fluids withat least substantially Newtonian viscosity properties is that jetting istypically achieved at shear rates around 1×10⁶ s⁻¹, while ink refillfrom the reservoir into the ink jet head channels takes place at100-1000 s⁻¹. A highly shear thinning ink will have much higherviscosity at the refill rate than at the jetting rate. This tends toslow down refill, compromising printhead performance. Shear thinningfluids can be avoided by formulating fluid compositions that exhibitlittle or no elasticity at the jetting temperature. Elasticity isminimized by controlling the amount and weight average molecular weightof oligo/resins incorporated into the fluid composition, by selectinghighly branched oligo/resins, and/or by manipulating the solubility ofthe higher molecular weight species in the formulation. Generally,formulations in which the oligo/resins are more soluble tend to be moreelastic than ones in which the oligo/resins are less soluble.

Compositions of the present invention also preferably have one or moreof several desirable features when cured. Firstly, preferred embodimentsof the present invention are compatible with an extremely wide varietyof porous and nonporous substrates. This is due, at least in part, tothe combinations of oligo/resin constituent(s) (for example, oligomersand/or polymers), monomer(s) of the reactive diluent and solvent(s). Theradiation curable fluid compositions also exhibit good adhesion tonon-porous substrates, especially those used in retroreflective sheetingtopfilms, when measured according to ASTM D 3359-95A Standard TestMethods for Measuring Adhesion by Tape Test, Method B.

Cured compositions of the present invention may have a wide range ofelongation characteristics depending upon the intended use. For example,such compositions may be characterized by an elongation of at leastabout 1%, preferably at least about 20%, more preferably from more thanabout 50% to about 300% or more, as desired. Cured compositions withelongation characteristics greater than about 50% are beneficially usedto reduce stress cracks, improve toughness, and improve weatherability.In the practice of the present invention, elongation of a cured materialrefers to the maximum elongation at break determined in accordance withASTM Test Method D-3759.

Cured compositions of the present invention also desirably arecharacterized by an elongation of at least about 50%, preferably atleast about 100%, more preferably from more than about 100% to about300%. Advantageously, cured compositions with such elongationcharacteristics are extremely beneficial in order to prevent the curedink layer from delaminating due to stretching or other dimensionalchange of the underlying substrate. Such elongation also allows thecured inks to more easily conform to contoured surfaces, such as thecontours and rivets on the panels of trucks or other vehicles.

Many embodiments of the radiation cured fluids of the present invention,excepting any containing opaque colorants such as carbon black, titania(TiO₂), or organic black dye, are transparent when measured according toASTM 810 Standard Test Method for Coefficient of Retroreflection ofRetroreflective Sheeting. That is, when coated onto retroreflectivesubstrates, the visible light striking the surface of such films istransmitted through to the retroreflective sheeting components. Thisproperty makes such inks particularly useful for outdoor signingapplications, in particular traffic control signing systems. Theradiation cured films of these liquid formulations are formulated andcured under conditions so as to exhibit tack-free surfaces when cured.This makes the printed images resistant to dirt build-up and the like.

In preferred embodiments, the cured films also resist marring whensubjected to moderate abrasion. A useful method for evaluating abrasionresistance is ASTM D 4060 Standard Test Method for Abrasion Resistanceof Organic Coatings by Taber Abraser. When monitored by percentretention of gloss or retroreflectivity over the abraded surfaces, thecured films of preferred embodiments show excellent abrasion resistancerelative to conventional screen printing ink standards.

The radiation cured films of preferred embodiments also exhibitdurability in outdoor applications, particularly when used as a systemwith retroreflective sheeting. Based upon direct comparison, these filmsexhibit comparable or improved durability relative to conventionalscreen printing ink standards.

Preferred radiation curable compositions of the present inventiongenerally incorporate (1) a radiation curable component comprising areactive diluent, optionally one or more macromers, optionally one ormore oligomers, and/or optionally one or more polymers, (2) a solventcomponent, and (3) one or more optional adjuvants that are selectedbased upon the intended use of the compositions. In the practice of thepresent invention, “radiation curable” refers to functionality directlyor indirectly pendant from a monomer, oligomer, or polymer backbone (asthe case may be) that participate in crosslinking reactions uponexposure to a suitable source of curing energy. Such functionalitygenerally includes not only groups that crosslink via a cationicmechanism upon radiation exposure but also groups that crosslink via afree radical mechanism. Representative examples of radiationcrosslinkable groups suitable in the practice of the present inventioninclude epoxy groups, (meth)acrylate groups, olefinic carbon—carbondouble bonds, allyloxy groups, alpha-methyl styrene groups,(meth)acrylamide groups, cyanate ester groups, vinyl ethers groups,combinations of these, and the like. Free radically polymerizable groupsare preferred. Of these, (meth)acryl moieties are most preferred. Theterm “(meth)acryl”, as used herein, encompasses acryl and/or methacryl.

The energy source used for achieving crosslinking of the radiationcurable functionality may be actinic (e.g., radiation having awavelength in the ultraviolet or visible region of the spectrum),accelerated particles (e.g., electron beam radiation), thermal (e.g.,heat or infrared radiation), or the like. Preferably, the energy isactinic radiation or accelerated particles, because such energy providesexcellent control over the initiation and rate of crosslinking.Additionally, actinic radiation and accelerated particles can be usedfor curing at relatively low temperatures. This avoids degradingcomponents that might be sensitive to the relatively high temperaturesthat might be required to initiate crosslinking of the curable groupswhen using thermal curing techniques. Suitable sources of actinicradiation include mercury lamps, xenon lamps, carbon arc lamps, tungstenfilament lamps, lasers, electron beam energy, sunlight, and the like.Ultraviolet radiation, especially from a medium pressure mercury lamp,is most preferred.

As used herein, the term “monomer” means a relatively low molecularweight (i.e., having a molecular weight less than about 500 g/mole)material having one or more polymerizable groups. “Oligomer” means arelatively intermediate molecular weight (i.e., having a molecularweight of from about 500 up to about 100,000 g/mole) material having oneor more polymerizable groups. “Polymer” means a molecule having asubstructure formed from one or more monomeric and/or oligomericconstituents and that has no further radiation curable group(s). Theterm “molecular weight” as used throughout this specification meansnumber average molecular weight unless expressly noted otherwise.

As used herein, the term “oligo/resin” shall be used to refercollectively to oligomers and polymers. Preferred oligo/resins have anumber average molecular weight below about 100,000, preferably fromabout 500 to about 30,000, and more preferably from about 700 to about10,000. One or more oligo/resins may be incorporated into fluidcompositions of the present invention in order to provide many benefits,including viscosity control, reduced shrinkage upon curing, durability,flexibility, adhesion to porous and nonporous substrates, outdoorweatherability, and/or the like. Oligo/resins suitable in the practiceof the present invention may be polyurethanes, acrylic materials,polyesters, polyimides, polyamides, epoxies, polystyrene, styrene andsubstituted styrene containing materials, silicone containing materials,fluorinated materials, combinations of these, and the like. Preferredoligo/resin materials are aliphatic in that aliphatic materials tend tohave good weatherability properties.

Optionally, one of the radiation curable monomers and/or theoligo/resins of the present invention may include functionality to helpenhance the performance of the fluid compositions of the presentinvention. For example, oligo/resins may include radiation curablefunctionality to allow these materials to co-crosslink with the reactivediluent upon exposure to a suitable energy source. To allow theoligo/resins to form an interpenetrating polymer network with thereactive diluent, oligo/resins may include a different kind ofcrosslinking functionality such as pendant hydroxyl groups or the like.In the presence of an isocyanate crosslinking agent, pendant hydroxylmoieties will undergo urethane crosslinking reactions with the NCOgroups of the isocyanate crosslinking agent to form a crosslinkednetwork comprising urethane linkages. To help disperse optionaladditives such as pigment colorants, inorganic powder fillers, and thelike, oligo/resins may comprise pendant dispersant moieties, such asacid or salt moieties of sulfonate, phosphate, phosphonate, carboxylate,polar heterocyclic, (meth)acrylonitrile, and/or the like.

For outdoor applications, polyurethane and acrylic-containingoligo/resins are preferred due to the tendency of these materials tohave excellent durability and weatherability characteristics. Suchmaterials also tend to be readily soluble in reactive diluents formedfrom radiation curable, (meth)acrylate functional monomers.

Because aromatic constituents of oligo/resins generally tend to havepoor weatherability and/or poor resistance to sunlight, aromaticconstituents are preferably limited to less than 5 weight percent,preferably less than 1 weight percent, and more preferably aresubstantially excluded from both the oligo/resins and the reactivediluents of the present invention. Accordingly, straight-chain, branchedand/or cyclic aliphatic and/or heterocyclic ingredients are preferredfor forming oligo/resins to be used in outdoor applications.

The oligo/resins themselves may be straight-chain, branched, and/orcyclic. Branched oligo/resins are preferred in that such materials tendto have lower viscosity than straight-chain counterparts of comparablemolecular weight. The amount of oligo/resin materials incorporated intofluid compositions of the present invention may vary within a wide rangedepending upon such factors as the intended use of the resultantcomposition, the nature of the reactive diluent, the nature to of theoligo/resin(s), the weight average molecular weight of the oligo/resins,and the like. As general guidelines ink jettable fluid compositions mayinclude from about 0.1 to about 50 weight percent of oligo/resins,wherein polymer species preferably may comprise from about 0.1 to about30, preferably 5 to about 20 weight percent of the composition. Oligomerspecies may comprise from about 0.1 to about 50, preferably from about15 to about 40 weight percent of the composition.

Suitable radiation curable oligo/resins for use in the present inventioninclude, but are not limited to, (meth)acrylated urethanes (i.e.,urethane (meth)acrylates), (meth)acrylated epoxies (i.e., epoxy(meth)acrylates), (meth)acrylated polyesters (i.e., polyester(meth)acrylates), (meth)acrylated (meth)acrylics, (meth)acrylatedsilicones, (meth)acrylated polyethers (i.e., polyether (meth)acrylates),vinyl (meth)acrylates, and (meth)acrylated oils.

Preferred (meth)acrylated aliphatic urethanes are di(meth)acrylateesters of hydroxy terminated isocyanato (—NCO) extended aliphaticpolyesters or aliphatic polyethers. (Meth)acrylated polyesters are thereaction products of (meth)acrylic acid with an aliphatic dibasicacid/aliphatic diol-based polyester. Examples of commercially available(meth)acrylated urethanes and polyesters include those known by thetrade designations PHOTOMER (Henkel Corp. of Hoboken, N.J.); EBECRYL284, 810, 4830, 8402, 1290, 1657, 1810, 2001, 2047, 230, 244, 264, 265,270, 4833, 4835, 4842, 4866, 4883, 657, 770, 80, 81, 811, 812, 83, 830,8301, 835, 870, 8800, 8803, 8804 (UCB Radcure Inc. of Smyrna, Ga.);SARTOMER CN series CN964 B-85, CN292, CN704, C 816, CN817, CN818, CN929,CN944B-85, CN945A-60, CN945B-85, CN953, CN961, CN962, CN963, CN 965,CN966, CN968, CN980, CN981, CN982, CN983, CN984, CN985 (Sartomer Co. ofExton, Pa.); ACTILANE (Akcross Chemicals of New Brunswick, N.J.); andUVITHANE (Morton International of Chicago, Ill.).

Preferred acrylated acrylics are acrylic oligomers or polymers that havereactive pendant or terminal (meth)acrylic acid groups capable offorming free radicals for subsequent reaction. Examples of commerciallyavailable (meth)acrylated acrylics include those known by the tradedesignations EBECRYL 745, 754, 767, 1701, and 1755 from UCB RadcureInc., Smyrna, Ga. Other oligo/resin examples include polymers availableunder the trade designations ELVACITE 2014 (ICI Acrylics, Inc.,Wilmington, Del.); JONCRYL 587 (S.C. Johnson, Racine, Wis.); andACRYLOID B series and PARALOID B series such as PARALOID B-60 (Rohm &Haas Co., Philadelphia, Pa.).

Another particularly preferred class of radiation curable, urethaneoligomers are described in Assignee's co-pending U.S. patent applicationfiled concurrently with the present application in the name of JamesCarlson et al. titled INKS AND OTHER COMPOSITIONS INCORPORATING LOWVISCOSITY, RADIATION CURABLE, POLYESTER URETHANE OLIGOMER, the entiredisclosure of which is incorporated herein by reference. These radiationcurable, urethane oligomers are generally characterized by atypicallylow viscosity characteristics, have a relatively high urethane content,are very economical to manufacture, and are compatible with a wide rangeof porous and nonporous substrates.

The reactive diluent generally comprises one or more radiation curablemonomers. Subject to desired performance standards, any radiationcurable monomer or combinations thereof may be incorporated into thereactive diluent. Accordingly, the present invention is not intended tobe limited to specific kinds of radiation curable monomers in variousaspects so long as any such performance conditions are satisfied.However, for ink jetting applications, such monomers, at least incombination, preferably exist as a liquid of ink jettable viscosity atthe desired ink jet head temperature.

The radiation curable monomers of the reactive diluent may be mono-,di-, tri-, tetra- or otherwise multifunctional in terms of radiationcurable moieties. These monomers function as diluents or solvents forthe oligo/resin component (if any), as viscosity reducers, as binderswhen cured, and as crosslinking agents. The amount of such monomers tobe incorporated into the reactive diluent can vary within a wide rangedepending upon the intended use of the resultant composition. As generalguidelines, the radiation curable component of the present invention maycontain from about 25 to about 100, preferably 40 to 90 weight percentof such monomers.

Representative examples of monofunctional, radiation curable monomerssuitable for use in the reactive diluent include styrene,alpha-methylstyrene, substituted styrene, vinyl esters, vinyl ethers,N-vinyl-2-pyrrolidone, (meth)acrylamide, N-substituted (meth)acrylamide,octyl (meth)acrylate, nonylphenol ethoxylate (meth)acrylate, isononyl(meth)acrylate, isobornyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate,β-carboxyethyl (meth)acrylate, isobutyl (meth)acrylate, cycloaliphaticepoxide, α-epoxide, 2-hydroxyethyl (meth)acrylate, (meth)acrylonitrile,maleic anhydride, itaconic acid, isodecyl (meth)acrylate, dodecyl(meth)acrylate, n-butyl (meth)acrylate, methyl (meth)acrylate, hexyl(meth)acrylate, (meth)acrylic acid, N-vinylcaprolactam, stearyl(meth)acrylate, hydroxy functional caprolactone ester (meth)acrylate,isooctyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxymethyl(meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyisopropyl(meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyisobutyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, combinations ofthese, and the like.

Multifunctional radiation curable materials may also be incorporatedinto the reactive diluent to enhance one or more properties of the curedfilm, including crosslink density, hardness, mar resistance, or thelike. If one or more of such multi functional materials are present, thereactive diluent may comprise from 0.5 to about 50, preferably 0.5 to35, and more preferably from about 0.5 to about 25 weight percent ofsuch materials. Examples of such higher functional, radiation curablemonomers include ethylene glycol di(meth)acrylate, hexanedioldi(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate,ethoxylated trimethylolpropane tri(meth)acrylate, glyceroltri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, and neopentylglycol di(meth)acrylate, combinationsof these, and the like.

Preferred radiation curable, reactive diluents of the present inventionmay be formulated with one or more radiation curable monomers orcombinations thereof that help the radiation curable compositions and/orresultant cured compositions to satisfy one or more desirableperformance criteria. For example, in order to promote hardness andabrasion resistance of resultant cured material, fluid compositions ofthe present invention advantageously may incorporate radiation curablemonomer(s) (hereinafter “high Tg component”) whose presence causes thecured material, or a portion thereof, to have a higher glass transitiontemperature, Tg, as compared to an otherwise identical material lackingsuch high Tg component. Preferred monomeric constituents of the high Tgcomponent generally include monomers whose homopolymer has a Tg of atleast about 50° C., preferably at least about 60° C., and morepreferably at least about 75° C. When used, the high Tg component mayconstitute 0.5 to 50, preferably 0.5 to 40, more preferably 0.5 to 30weight percent of the radiation curable, reactive diluent.

An exemplary class of radiation curable monomers that tend to haverelatively high Tg characteristics suitable for incorporation into thehigh Tg component generally comprise at least one radiation curable(meth)acrylate moiety and at least one alicyclic and/or heterocyclicmoiety. Isobornyl (meth)acrylate is a specific example of one suchmonomer. A a cured, homopolymer film formed from isobornyl acrylate, forinstance, has a Tg of 88° C. The monomer itself has a molecular weightof 208 g/mole, exists as a clear liquid at room temperature, has aviscosity of 9 centipoise at 25° C., has a surface tension of 31.7dynes/cm at 25° C., and is an excellent reactive diluent for many kindsof oligo/resins. In the practice of the present invention, Tg of amonomer refers to the glass transition temperature of a cured film of ahomopolymer of the monomer, in which Tg is measured by differentialscanning calorimetry (DSC) techniques.

In order to promote adhesion both before and especially after radiationcuring, fluid compositions of the present invention advantageously mayincorporate radiation curable monomer(s) (hereinafter “adhesionpromoting component”) whose presence causes the uncured and/or curedmaterial to have higher adhesion to the desired receiving substrate ascompared to an otherwise identical formulation lacking such adhesionpromoting component. Preferred monomeric constituents of the adhesionpromoting component generally include monomers having an adhesion scoreof at least about 50, preferably at least about 80, and more preferablyat least about 95 when measured according to ASTM D 3359-95A StandardTest Methods for Measuring Adhesion by Tape Test, Method B. When used,the adhesion promoting component may comprise 0.5 to about 70,preferably 0.5 to about 50, more preferably 0.5 to about 40 weightpercent of the reactive diluent.

A wide variety of monomers with adhesion promoting characteristics maybe incorporated singly or in combination into the adhesion promotingcomponent of the reactive diluent. Adhesion promoting monomers are thosethat tend to diffuse into the substrate to form a physical lock whencured. Such monomers have a measurable diffusion coefficient into thesubstrate of interest. One such class of monomers comprises one or more(meth)acrylate moieties and one or more alkoxy and/or polyalkoxymoieties. These alkoxylated monomers tend to be characterized by goodflexibility, low shrinkage, and impact strength when cured. However, thealkoxy or polyalkoxy moieties of such materials may have a tendency tooxidize over time. This could impair the performance of the resultantcured material, particularly if the alkoxylated functionality issituated in the monomer such that such functionality is positioned aspart of a main polymer backbone when the compositions of the presentinvention are cured. These materials also are compatible only with alimited range of nonporous substrates.

Accordingly, it is preferred to limit the use of alkoxylated monomerscomprising such main chaing alkoxylated functionality, and preferredreactive diluents comprise no more than about 30 weight percent of suchalkoxylated monomers. Limiting the use of alkoxylated monomers for whichthe alkoxylated functionality becomes pendant from a main polymerbackbone is generally not required in the practice of the presentinvention. Oxidation of such pendant alkoxylated functionality has lessof an impact upon bulk polymer properties than does oxidation of mainchain alkoxylated functionality.

A specific example of one illustrative alkoxylated monomer is2-(2-ethoxyethoxy)ethyl acrylate. This monomer is a clear liquid at roomtemperature and has a viscosity of 6 centipoise at 25° C., a surfacetension of 32.4 dynes/cm at 25° C., and is slightly polar. A homopolymerof this monomer has a Tg of −54° C.

Another class of radiation curable monomers with adhesion promotingcharacteristics suitable for use in the adhesion promoting componentinclude relatively low Tg monomers comprising at least one heterocyclicmoiety and at least one (meth)acrylate moiety. As used herein, low Tgmeans that a cured homopolymer film of the monomer has a Tg of less thanabout 40° C., preferably less than about 10° C., and more preferablyless than about −10° C. An illustrative embodiment of one such monomeris tetrahydrofurfuryl acrylate. This monomer is an excellent adhesionpromoter with respect to many different kinds of porous and nonporoussubstrates, is a clear liquid at room temperature, has a viscosity of 6centipoise at 25° C., a surface tension of 36.1 dynes/cm at 25° C., a Tgof −28° C., and a molecular weight of 156 g/mole.

Combinations of monomers with adhesion promoting characteristics areadvantageously used to formulate an adhesion promoting component of thepresent invention. One particularly preferred combination with goodadhesion promoting properties comprises 1 to 10 parts by weight of analkoxylated (meth)acrylate per 5 to 15 parts by weight of a heterocyclic(meth)acrylate. A particularly preferred embodiment of such acombination comprises 2-(2-ethoxyethoxy)ethyl (meth)acrylate andtetrahydrofurfuryl (meth)acrylate.

In many applications, printing features with good initial gloss and goodgloss retention over time is important. For such applications, it may bedesirable to incorporate one or more monomers (hereinafter glosscomponent) into the reactive diluent whose presence provides cured,printed features with better initial gloss and or gloss retention ascompared to otherwise identical films lacking such gloss component.Preferred radiation curable reactive diluents comprise a sufficientamount of a gloss component such that a cured, homopolymer film of thematerial has a 60° gloss of at least 70, preferably at least 90, whenmeasured according to ASTM D 523 Standard Test Method for SpecularGloss. When a gloss component is used, reactive diluents may comprise0.5 to 30, preferably 0.5 to 15, more preferably 0.5 to 10 weightpercent of the gloss component.

A wide variety of suitable monomers may be incorporated singly or incombination into the gloss component. One such class of monomerscomprises radiation curable monomers that are solids at roomtemperature. Although solids by themselves, such monomers tend to bereadily soluble in one or more of the other monomers constituting thereactive diluent. Thus, these solid, gloss promoting materials areeasily included in ink jettable formulations. A specific example of sucha monomer is N-vinyl caprolactam. This monomer is a solid up to about34° C., has a viscosity of 2.88 centipoise at 50° C., and a flash pointof 114° C.

In some instances, one or more monomers incorporated into the reactivediluent may have beneficial properties in one regard, yet may have poorwetting characteristics in terms of being able to wet a wide range ofdifferent kinds of porous and nonporous substrates. Tetrahydrofurfurylacrylate is a good example of this. This monomer has excellent adhesivecharacteristics, but limited wetting characteristics. Accordingly, insuch instances if desired, it may be desirable to incorporate one ormore monomers (enhanced wetting component) into the reactive diluentwhose presence causes the radiation curable fluid composition to havebetter wetting properties for the desired substrate(s) as compared to anotherwise identical composition lacking such a component. Preferredconstituents of the enhanced wetting component preferably comprise oneor more monomers respectively having surface tension properties of about30 dynes/cm or less.

A wide variety of monomers with such low surface tension properties maybe incorporated singly or in combination into the enhanced wettingcomponent. One such class of monomers comprises at least one(meth)acrylate moiety and at least one aliphatic moiety that is straightchained or branched. A specific example of this class of monomers isisooctyl acrylate. This monomer is a clear liquid at room temperature,has a molecular weight of 184 g/mole, and has a surface tension of 28dynes/cm.

There are several representative examples of specific embodiments ofradiation curable, reactive diluent formulations of the presentinvention that advantageously incorporate one or more of the reactivediluent components described above. For example, one such reactivediluent embodiment comprises 10 to 40 weight percent of the high Tgcomponent (preferably isobornyl (meth)acrylate), 15 to 50 weight percentof the adhesion promoting component (preferably a combination of 1 to 20parts by weight of 2(2-ethoxyethoxy)ethyl (meth)acrylate per 1 to 20parts by weight of tetrahydrofurfuryl (meth)acrylate), 5 to 10 weightpercent of the gloss component (preferably N-vinylcaprolactam), 5 to 20weight percent of a multifunctional radiation curable monomer(preferably 1,6-hexanediol di(meth)acrylate), and 5 to 20 weight percentof the low surface tension component (preferably isooctyl(meth)acrylate).

Another illustrative, preferred reactive diluent of the presentinvention comprises 30 to 50 weight percent of a high Tg component(preferably isobornyl (meth)acrylate), 30 to 50 weight percent of aadhesion promoting component (preferably 2-(2-ethoxyethoxy)ethyl(meth)acrylate and/or tetrahydrofurfuryl (meth)acrylate), and 5 to 15weight percent of a multifunctional radiation curable monomer(preferably 1,6-hexanediol di(meth)acrylate).

Radiation curable ink compositions of the present invention alsoadvantageously incorporate a limited, moderate amount of a solventcomponent with low surface tension properties. Preferred solventsdesirably have a surface tension that is no more than about, andpreferably at least about 2 dynes/cm less than, the surface tension ofthe reactive diluent taken as a whole; provided, however, that the morepreferred solvents additionally have a surface tension that is less thanabout 30 dynes/cm at 25° C., preferably less than about 28 dynes/cm at25° C., and more preferably less than about 26 dynes/cm at 25° C. Thepreferred solvents also desirably have a relatively high flash point ofat least about 50° C., preferably at least about 60° C.

The compositions desirably include enough solvent to promote the desiredlevel of wetting and adhesion, to reduce the viscosity of thecomposition to a level suitable for ink jetting applications, to reducethe surface tension of the composition to the necessary level to wet awide variety of substrates, and/or to provide a vapor barrier that formsover printed compositions in situ during radiation curing to improve thequality of the cure. So long as enough solvent is present to promote oneor more of these objectives as desired, using lesser amounts of solventtends to provide better quality printed features as compared to usinggreater amounts of solvent. Using more solvent than is needed may alsoincrease the difficulty of drying the printed features during radiationcuring and could deteriorate the cured image appearance and properties.As general guidelines, radiation curable ink compositions of the presentinvention may comprise 0.1 to 40, preferably 0.5 to 15, more preferably1 to about 10 weight percent of the solvent component.

The solvent component may comprise one or more solvents that may beaqueous or inorganic, polar or nonpolar, or the like. Organic solventsthat are polar or nonpolar are more preferred inasmuch as such solventstend to dry more readily during radiation curing. Preferred organicsolvents also promote compatibility with a wide range of polymersubstrates by reducing the surface tension of the ink to the desiredlevel. Also, preferred solvents should be compatible with the pigmentdispersion so that the solvent does not cause ink instability. Asanother desirable characteristic, solvents of the present invention aredesirably liquids at the print head temperature and undergosubstantially no polymerization through free radical polymerizationmechanisms when radiation curable components of the formulations areradiation cured.

It can be appreciated, therefore, that a wide range of solvents may beincorporated into the solvent component. Representative examples includewater; alcohols such as isopropyl alcohol (IPA) or ethanol; ketones suchas methyl ethyl ketone, cyclohexanone, or acetone; aromatichydrocarbons; isophorone; butyrolactone; N-methyl pyrrolidone;tetrahydrofuran; ethers such as lactates, acetates, and the like; estersolvents such as propylene glycol monomethyl ether acetate (PM acetate),diethylene glycol ethyl ether acetate (DE acetate), ethylene glycolbutyl ether acetate (EB acetate), dipropylene glycol monomethyl acetate(DPM acetate), iso-alkyl esters, isohexyl acetate, isoheptyl acetate,isooctyl acetate, isononyl acetate, isodecyl acetate, isododecylacetate, isotridecyl acetate or other iso-alkyl esters; combinations ofthese and the like.

Esters, particularly those comprising branched aliphatic moieties suchas iso-alkyl moieties, are one class of preferred solvents. Thesesolvents provide numerous advantages when incorporated into radiationcurable ink jet inks. First, these solvents are compatible with all ofthe nonporous, polymeric substrates currently in widespread use in thesign making industry. The materials are also excellent solvents for theradiation curable monomers, oligomers, and polymers. Uniquely, thesematerials evaporate very easily, yet have relatively high flash points.Thus, these solvents are easily removed during radiation curing, yet donot significantly reduce the formulation flash point. Ink compositionsincluding these solvents also have very favorable dot gaincharacteristics. A variety of branched, aliphatic ester solvents arecommercially available under the trade designation “EXXATE” fromExxonMobil Corp. of Irving, Tex.

In preferred embodiments, relatively polar solvents such as isopropylalcohol are less desirable than relatively nonpolar solvents in thatpolar solvents may have a strong affinity for the dispersants, if any,used to stabilize the pigment in the inks. This affinity can causepigment agglomeration and ink destabilization. Solvents with staticsurface tension at 25° C. of greater than about 30 dynes/cm also areless preferred.

In addition to the radiation curable component and the solvent, one ormore other additives may be incorporated into compositions of thepresent invention in accordance with conventional practices. Theseoptional additives include one or more of photoinitiators, colorants,slip modifiers, thixotropic agents, foaming agents, antifoaming agents,flow or other rheology control agents, waxes, oils, plasticizers,binders, antioxidants, photoinitiator stabilizers, electrical conductiveagents, fungicides, bactericides, organic and/or inorganic fillerparticles, leveling agents, opacifiers, antistatic agents, dispersants,and the like.

The pigment used in the ink composition provides the desired color.Durable pigments are preferred for use in the inks of the invention,meaning that they have good outdoor durability and resist fading uponexposure to sun and the elements.

Pigments useful in the invention may be organic or inorganic. Suitableinorganic pigments include carbon black and titania (TiO₂), whilesuitable organic pigments include phthalocyanines, anthraquinones,perylenes, carbazoles, monoazo- and disazobenzimidazolone,isoindolinones, monoazonaphthol, diarylidepyrazolone, rhodamine,indigoid, quinacridone, diazopyranthrone, dinitraniline, pyrazolone,dianisidine, pyranthrone, tetrachloroisoindolinone, dioxazine,monoazoacrylide, anthrapyrimidine. It will be recognized by thoseskilled in the art that organic pigments will be differently shaded, oreven have different colors, depending on the functional groups attachedto the main molecule.

Commercial examples of useful organic pigments include those knowndescribed in The Colour Index, Vols. 1-8, Society of Dyers andColourists, Yorkshire, England having the designations Pigment Blue 1,Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue15:3, Pigment Blue 15:4, Pigment Blue 15:6, Pigment Blue 16, PigmentBlue 24, and Pigment Blue 60 (blue pigments); Pigment Brown 5, PigmentBrown 23, and Pigment Brown 25 (brown pigments); Pigment Yellow 3,Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow24, Pigment Yellow 65, Pigment Yellow 73, Pigment Yellow 74, PigmentYellow 83, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 108,Pigment Yellow 109, Pigment Yellow 110, Pigment Yellow 113, PigmentYellow 128, Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 139,Pigment Yellow 150, Pigment Yellow 154, Pigment Yellow 156, and PigmentYellow 175 (yellow pigments); Pigment Green 1, Pigment Green 7, PigmentGreen 10, and Pigment Green 36 (green pigments); Pigment Orange 5,Pigment Orange 15, Pigment Orange 16, Pigment Orange 31, Pigment Orange34, Pigment Orange 36, Pigment Orange 43, Pigment Orange 48, PigmentOrange 51, Pigment Orange 60, and Pigment Orange 61 (orange pigments);Pigment Red 4, Pigment Red 5, Pigment Red 7, Pigment Red 9, Pigment Red22, Pigment Red 23, Pigment Red 48, Pigment Red 48:2, Pigment Red 49,Pigment Red 112, Pigment Red 122, Pigment Red 123, Pigment Red 149,Pigment Red 166, Pigment Red 168, Pigment Red 170, Pigment Red 177,Pigment Red 179, Pigment Red 190, Pigment Red 202, Pigment Red 206,Pigment Red 207, and Pigment Red 224 (red pigments); Pigment Violet 19,Pigment Violet 23, Pigment Violet 37, Pigment Violet 32, and PigmentViolet 42 (violet pigments); and Pigment Black 6 or 7(black pigments).

The pigment is generally incorporated into the ink composition bymilling the pigment into selected reactive monomers and optionaloligo/resin materials. If the ink is to be used in applications whereinthe ink is used in combination with a retroreflective backing, thepigment must be milled to a particle size that provides sufficienttransparency to permit retroreflection and provide retroreflectivecolor. This may be accomplished, for example, by milling the pigment.

If a colorant in the form of pigment is used, a dispersant may bedesired in some instances in order to stabilize the pigment. The choiceof dispersant depends on factors such as the type of pigment used, thetype of oligo/resin(s) in the formulation, the composition of thephase(s) into which the pigment will be dispersed, and the like.Examples of commercially available dispersants suitable for thisapplication include those sold under the trade designations SOLSPERSEfrom Zeneca of Wilmington, Del.; EFKA from Lubrizol Corp. of Wickliff,Ohio; and BYK from BYK-Chemie USA of Wallingford, Conn.

It is possible to use mixtures of dispersants also. The amount ofdispersant added depends on the type and concentration of the pigment.Typically 20 to 100 parts by weight of dispersant are used per 100 partsby weight of organic pigment, and between 5 to 80 parts by weight of thedispersant per 100 parts by weight inorganic pigment.

In the preferred mode of the invention, the inks are cured using UVradiation, which typically benefits from the presence of at least onephotoinitiator. The type of photoinitiator used depends on the choice ofcolorant in the ink and on the wavelength of the radiation. Commerciallyavailable free-radical generating photoinitiators suitable for theinvention include, but are not limited to benzophenone, benzoin etherand acylphosphine photoinitiators such as those sold under the tradedesignations IRGACURE and DAROCUR from Ciba-Geigy Corp. of Ardsey, N.Y.

In addition, the colorant in the ink will absorb part of the incidentradiation, depleting the available energy to activate thephotoinitiator(s). This will slow down the curing rate and may result inpoor through and/or surface cure of the applied ink. It is thereforepreferred to use a mixture of photoinitiators in order to provide bothsurface and through cure. The amount of photoinitiator(s) used typicallyvaries between 1 and 15 weight percent and preferably between 3 and 12weight percent and more preferably between 5 and 10 weight percent forformulations containing colorant. The uncolored inks can have lowerinitiator concentrations. Co-initiators and amine synergists can beincluded in order to improve curing rate. Examples includeisopropylthioxanthone, ethyl 4-(dimethylamino)benzoate, 2-ethylhexyldimethylaminobenzoate, and dimethylaminoethyl methacrylate.

To enhance durability of a printed image graphic, especially in outdoorenvironments exposed to sunlight, a variety of commercially availablestabilizing chemicals can be added optionally to inks of the presentinvention. These stabilizers can be grouped into the followingcategories: heat stabilizers; ultra-violet light stabilizers; andfree-radical scavengers. Heat stabilizers are commonly used to protectthe resulting image graphic against the effects of heat and arecommercially available under the trade designations MARK V 1923 (WitcoCorp. of Greenwich, Conn.); SYNPRON 1163, Ferro 1237 and Ferro 1720(Ferro Corp., Polymer Additives Div., Walton Hills, Ohio). Such heatstabilizers can be present in amounts ranging from about 0.02 to about0.15 weight percent.

Ultraviolet light stabilizers are commercially available under the tradedesignations UVINOL 400 (a benzophenone type uv-absorber sold by BASFCorp. of Parsippany, N.J.); Cyasorba UV164 from Cytec Industries, WestPatterson, N.J.; and TINUVIN 900 and/or 1130 UV-absorber (Ciba SpecialtyChemicals, Tarrytown, N.Y.) and can be present in amounts ranging fromabout 0.1 to about 5 weight percent of the total ink.

Free-radical scavengers can be present in an amount from about 0.05 toabout 2.5 weight percent of the total ink. Nonlimiting examples of thescavenger include hindered amine light stabilizer (HALS) compounds,hydroxylamines, sterically hindered phenols, and the like.

Commercially available HALS compounds include TINUVIN 292 (tradedesignation for a hindered amine light stabilizer sold by Ciba SpecialtyChemicals, Tarrytown, N.Y.) and CYASORB UV3581 (trade designation for ahindered amine light stabilizer sold by Cytec Industries, WestPatterson, N.J.).

Optionally, the composition may include one or more additives in orderto adjust the electrical conductivity of the composition. For example,as one suggested range that may be preferred for some applications, theelectrical conductivity of the composition may be adjusted such that theelectrical resistivity is below 5000 ohm-cm, preferably below about 500ohm-cm. In accordance with the present invention, an ink shall be deemedto be conductive if it has an electrical resistivity in this range. Ifoutside this range, such an ink will be deemed to be substantiallynonconductive. If present, conductive agents are typically present inamounts up to about 2 weight percent. Examples include dimethylaminehydrochloride, diethylamine hydrochloride, lithium nitrate, andhydroxylamine hydrochloride.

In some applications, such as certain forms of ink jet printing,substantially nonconductive inks are required for good performance. Forsuch applications, ink compositions of the present invention preferablyare substantially nonconductive.

The compositions of the present invention are made by mixing togetherthe desired ingredients using any suitable technique. For example, in aone step approach, all of the ingredients are combined and blended,stirred, milled, or otherwise mixed to form a homogeneous composition.As another alternative, at least some of the components of the radiationcurable component and at least some of the solvent may be blendedtogether in a first step. Then, in one or more additional steps, theremaining solvent if any, the remaining constituents of the radiationcurable component if any, and one or more additives may be incorporatedinto the composition via blending, milling, or other mixing technique.

As still yet another approach which is particularly preferred whenpigment colorants are to be included in the radiation curable, fluidcompositions, a preferred processing approach involves preparing thecomposition such that the pigment particle size of the colorant is lessthan 5 micrometers, preferably less than 1 micron, ideally less than 0.5micrometers. The particle size of the pigment colorant may becharacterized by an appropriate method such as dynamic light scattering(DLS) or microscopy. We have found that ink jettable compositionscomprising such fine pigment colorants provide excellent colorsaturation, transparency, and jettability, especially for applicationsin which the composition is a colored ink that is printed ontoretroreflective signage of outdoor signage.

Initially, a dispersion is prepared containing from about 1 to about 80weight percent of the pigment colorant with the balance being theoligo/resin, reactive diluent, and other additives, if desired. At thisstage, the pigment may be incorporated into the dispersion as suppliedby the vendor. Subsequent milling will reduce the pigment size to thedesired fine particle size. This initial dispersion may be prepared byfirst predissolving a dispersant in the liquid components and thenadding the desired amount of pigment powder. Initial wetting of pigmentis accomplished with high shear mixing. Next, the dispersion issubjected to high energy milling techniques such as ball milling, sandmilling, horizontal media milling, attritor milling, or 2- or 3-rollmilling, or the like in order to reduce the pigment to the desiredparticle size. Following the milling, the resultant ink dispersion isexceptionally stable (i.e. the dispersion remains homogeneous andparticle size does not increase over long periods of time, e.g., 26weeks). Following the milling procedure, the pigment dispersion may bediluted with additional solvents, monomers, oligomers, polymers,dispersants, flow agents, surfactants, photoinitiators, UVA, HALS,and/or the like. The millbase also remains stable following the additionand incorporation of these additional components. Detailed teaching ofpigment milling and millbase let down can be found in Patton, “PaintFlow and Pigment Dispersion”, ISBN #0-471-03272.

The compositions of the present invention may be applied in any suitablefashion onto a receiving substrate such as wood, metal, paper, woven ornonwoven fabrics, resin-coated paper, foil, polymer articles, polymerfilms, and the like. Representative examples of coating techniquesinclude screen printing, spraying, ink jetting, extrusion-die coating,flexographic printing, offset printing, gravure coating, knife coating,brushing, curtain coating, wire-wound rod coating, bar coating and thelike. The compositions of the present invention may be used to formgraphic elements, text items, continuous layers, bar codes, or otherfeatures.

Compositions of the present invention are highly compatible with bothporous and nonporous substrates. The compatibility with nonporousmaterials allows these compositions to be applied onto a wide range ofnonporous polymer films. Nonlimiting examples of such films includesingle and multi-layer constructions of acrylic-containing films,poly(vinyl chloride)-containing films, (e.g., vinyl, plasticized vinyl,reinforced vinyl, vinyl/acrylic blends), urethane-containing films,melamine-containing films, polyvinylbutyral-containing films, andmulti-layered films having an image reception layer comprising an acid-or acid/acrylate modified ethylene vinyl acetate resin, as disclosed inU.S. Pat. No. 5,721,086 (Emslander et al.) or having an image receptionlayer comprising a polymer comprising at least two monoethylenicallyunsaturated monomeric units, wherein one monomeric unit comprises asubstituted alkene where each branch comprises from 0 to about 8 carbonatoms and wherein one other monomeric unit comprises a (meth)acrylicacid ester of a nontertiary alkyl alcohol in which the alkyl groupcontains from 1 to about 12 carbon atoms and can include heteroatoms inthe alkyl chain and in which the alcohol can be linear, branched, orcyclic in nature.

Such films have two major surfaces with one surface being able toreceive an inkjet image graphic of the present invention and the othermajor surface being adhered to a field of pressure sensitive adhesive.Usually, the field of adhesive on one major surface is protected by arelease liner. Such films can be clear, translucent, or opaque. Suchfilms can be colorless or solid color or a pattern of colors. Such filmscan be transmissive, reflective, or retroreflective.

Commercially available films known to those skilled in the art includethe multitude of films available from 3M Company under the tradedesignations PANAFLEX, NOMAD, SCOTCHCAL, SCOTCHLITE, CONTROLTAC, andCONTROLTAC-PLUS.

After being coated, the compositions may be cured using a suitablefluence and type of curing energy. The amount of curing energy to beused for curing depends upon a number of factors, such as the amount andthe type of reactants involved, the energy source, web speed, thedistance from the energy source, and the thickness of the material to becured. Generally, the rate of curing tends to increase with increasedenergy intensity. The rate of curing also may tend to increase withincreasing amounts of photocatalyst and/or photoinitiator being presentin the composition. As general guidelines, actinic radiation typicallyinvolves a total energy exposure from about 0.1 to about 10 J/cm², andelectron beam radiation typically involves a total energy exposure inthe range from less than 1 megarad to 100 megarads or more, preferably 1to 10 Mrads. Exposure times may be from less than about 1 second up to10 minutes or more. Radiation exposure may occur in air or in an inertatmosphere such as nitrogen.

The present invention will now be further described with reference tothe following illustrative examples.

Test Methods Used in the Examples

Viscosity was measured either using a Brookfield viscometer or by usinga Rheometrics SR-200 (Rheometric Scientific, Inc. of Piscataway, N.J.)controlled stress rheometer with the cup and bob geometry. The viscositydependence on shear rate and temperature was recorded. For shearthinning samples, it was assumed that the viscosity as measured at 1000s⁻¹ was the same as the viscosity during jetting.

The power law index was calculated from measurement of the shearthinning behavior of the sample.

Static surface tension was measured at room temperature using a KrussK-12 processor tensiometer (available from Kruss GmbH of HamburgGermany) using the plate method.

Percent elongation of cured films was determined according to ASTM TestMethod D-5035

Contact angle measurements (advancing) were carried out using agoniometer from Rame-Hart, Inc. of Mountain Lakes, N.J.

Wetting and flow rating were judged by eye. A rating of 0 indicatedperfect wetting and flow at one end of the scale, while a rating of 3indicated very poor wetting and flow at the other end of the scale.

Adhesion was measured by crosshatch method according to ASTM D 3359-95AStandard Test Methods for Measuring Adhesion by Tape Test, Method B.

The Following Abbreviations are used Throughout the Examples:

cP centipoise; THFFA tetrahydrofurfuryl acrylate; IBOA isobornylacrylate; EEEA 2-(2-ethoxyethoxy)ethyl acrylate; HDDA hexanedioldiacrylate; IOA isooctyl acrylate; NVC N-vinylcaprolactam; Diamond Grade3M SCOTCHLITE DIAMOND GRADE LDP REFLECTIVE SHEETING SERIES 3970retroreflective film available from 3M Company; 3540C film 3M CONTROLTACPLUS GRAPHIC MARKING FILM WITH COMPLY ™ PERFORMANCE 3540C (SCREENPRINTING) available from 3M Company; 180-10 vinyl 3M CONTROLTAC PLUSGRAPHIC SYSTEM 180-10 vinyl film available from 3M Company; SF96-100SILICONE SF96-100, a trade designation for a silicone flow agentavailable from General Electric Corp. of Schenectady, NY; IPTXisopropylthioxanthone commercially available under the trade designationSPEEDCURE ITX from Aceto Corp. of New Hyde Park, NY.

The Following Additional Materials were used in the Examples:

Oligomer A was prepared according to the following procedure: 60 gpolycaprolactone acrylate (molecular weight 344, 0.174 equivalents,Aldrich Chemical Co. of Milwaukee, Wis.) was added to 200 mg BHT and 1drop dibutyltin dilaurate. This was heated under an atmosphere of dryair to 45° C. 24 g VESTANAT TMDI (trade designation for a mixture of2,2,4-trimethyl hexamethylene diisocyanate and2,4,4-trimethylhexamethylene diisocyanate, 0.236 equivalents, availablefrom Creanova Inc. of Somerset, N.J.) was added slowly, controlling theexotherm to under 55° C. After a 2 hour hold at 50° C, 11.1 g TONE 0305polycaprolactone triol having 550 molecular weight available from UnionCarbide Corp. of Danbury, Conn., (0.062 equivalents) was added alongwith 2 drops dibutyltin dilaurate. The reaction was held at 50° C. for48 hours, adding 2 drops of dibutyltin dilaurate at the 24 hour mark.After this, the infrared spectrum showed a small amount of residualisocyanate which was consumed by adding 1 g ethanol and holding for 2hours. The Brookfield viscosity of the product was determined to be 9000cp at 25° C. Calculated molecular weight data: M=1250, M_(w)=2100. Gelpermeation chromatography results: M_(n)=1380, M_(w)=2480.

Oligomer B was prepared according to the following procedure: 281.3 gTONE M-100 polycaprolactone acrylate, available from Union Carbide Corp.of Danbury, Conn., (0.818 equivalents) was added to 0.040 g2,6-di-tert-butyl-4-methyl phenol (BHT) and 1 drop dibutyltin dilaurate(both available from Aldrich Chemical Co. of Milwaukee, Wis.). This washeated with stirring under an atmosphere of dry air to 90° C. 84.2 gVESTANAT TMDI (trade designation for a mixture of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylenediisocyanate, 0.80 equivalents, available from Creanova Inc. ofSomerset, N.J.) was added slowly, controlling the exotherm to under 100°C. with a water bath. The reaction was held at 90° C. for 8 hours,whereupon the IR spectrum showed no residual isocyanate. The Brookfieldviscosity of the product was determined to be 2500 cp at 25° C. Thecalculated molecular weight of this material was 875.

BAYER YELLOW Y5688 is a trade designation for a yellow pigment availablefrom Bayer Corp. of Pittsburgh, Pa.

RT-343-D magenta pigment is a trade designation for magenta pigmentavailable from Ciba Specialty Chemicals of Tarrytown, N.Y.

249-1284 Cyan 15:3 Pigment is a trade desgniation for cyan pigmentavailable from Sun Chemical Corp. of Fort lee, N.J.

LAMPBLACK LB 101 PIGMENT I is a trade designation for black pigmentavailable from Pfizer Inc. of New York, N.Y.

STABAXOL I is a trade designation for 2,2′, 6,6′-tetraisopropyldiphenylcarbodiimide available from Rhein Chemie Corp. of Trenton, N.J.

IRGACURE 819 is a trade designation forbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, IRGACURE 651 is atrade designation for 2,2-dimethoxy-1,2-diphenylethan-1-one, andIRGACURE 369 is a trade designation for2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one all arephotoinitiators available from Ciba Specialty Chemicals of Tarrytown,N.Y.

SOLSPERSE 5000 and SOLSPERSE 32000 are trade designations fordispersants available from Zeneca Inc of Wilmington, Del.

SR368 is a trade designation for tris (2-hydroxy ethyl)isocyanuratetriacrylate, and PRO-4303 is a trade designation for a mixture of 10weight percent THFFA, 16 weight percent SR368, and 74 weight percent ofCN983, an aliphatic polyester based urethane diacrylate, both availablefrom Sartomer Co. of Exton, Pa.

EBECRYL 284 is a trade designation for aliphatic urethane diacrylatediluted 12% with hexanediol diacrylate available from UCB Chemicals ofSmyrna, Ga.

Tetrahydrofurfuryl acrylate, isobomyl acrylate, 2-(2-ethoxyethoxy)ethylacrylate, hexanediol diacrylate, isooctyl acrylate andN-vinylcaprolactam are available from Sartomer Co. of Exton, Pa.

IRGANOX 1035 and TINUVIN 292 are trade designations for stabilizersavailable from Ciba Specialty Chemicals of Tarrytown, N.Y.

P-M ACETATE is a trade designation for propylene glycol monomethyl etheracetate available from Eastman Chemical Co. of Kingsport, Tenn.

MINI-ZETA is a trade designation for a bead mill available from millNetzsch Inc. of Exton, Pa.

XAAR XJ128-200 and XAAR XJ128-360 printheads were obtained from XaarLimited of Cambridge, England.

PIXEL JET is a trade designation for a 64 channel inkjet printheadavailable from Trident International of Brookfield, Conn.

EXAMPLE 1

This example describes the preparation of yellow, UV curable inks (InkA1, comparative and Ink B1 of the present invention).

A yellow millbase (Millbase A) was prepared by milling 40 parts Bayeryellow Y5688, 25 parts Solsperse 32000 and 35 parts THFFA for 70 minutesusing a Netzsch Mini-Zeta bead mill with 0.5 mm zirconia media.

Ink A1 (comparative) was prepared by combining the followingingredients: 20 parts yellow Millbase A, 100 parts Oligomer A, 40 partsNVC, 75 parts THFFA, 75 parts IBOA and 75 parts EEEA. These were mixedon rollers for 24 hrs.

Ink B1 was prepared by combining with mixing 120 parts ink A1 and 10parts PM ACETATE (surface tension was 27.4 dyne/cm at 25° C.). Thesolvent content of Ink B1 was 7.7 percent by weight.

Surface tension and viscosity of the two inks are shown in Table 1.

TABLE 1 Property Ink A1 (comparative) Ink B1 Viscosity (cP) 27.6 19.1Surface tension (dynes/cm) 33.6 32.6

Jetting performance of both inks was evaluated using an a XAAR XJ128-200piezo ink jet printhead. Ink A1 had an average drop velocity of 3.35 m/swhile ink B1 had an average drop velocity of 4.0 m/s. Since jetting wasat room temperature, and since Ink A1 had a higher viscosity than InkB1, this result was expected.

To eliminate the effect of viscosity on jetting performance a TridentPixel jet printhead was used. This printhead can be heated so that thetwo inks may be jetted at the same viscosity. Ink A1 was jetted at 45.2°C. and Ink B1 was jetted at 37.3° C. At these temperatures, both inkshad a viscosity of 12 cP. When jetting performance was examined at thesetemperatures, both inks performed similarly in terms of the dropvelocity and satellite drop formation. The results indicate that addedsolvent does not have negative effect on jetting performance, and forroom temperature jetting, it improves jetting performance by loweringthe viscosity.

EXAMPLE 2

This example shows that added solvent improves cured film hardness andmar resistance.

Photoinitiator was added to both Ink A1 and Ink B1 according to thefollowing 20 formulations:

100 parts Ink A1, 3 parts IRGACURE 819, 2 parts IRGACURE 651, 1 partsIPTX, 0.5 parts IRGACURE 369 (Ink A2, comparative).

100 parts Ink B1, 3 parts IRGACURE 819, 2 parts IRGACURE 651, 1 partsIPTX, 0.5 parts IRGACURE 369 (Ink B2).

The inks were printed on an x-y positionable platen using an XAARXJ128-200 printhead at 200×300 dpi resolution solid fill image on 180-10vinyl film. Ink A2 printed poorly, and a few nozzles stopped firingduring printing. In contrast, Ink B2 printed very well giving a uniformglossy image

The printed films were cured using a Fusion UV Systems processor (mediumpressure mercury bulbs, Rockville, Md.) at 240 mJ/cm² exposure. Bothsamples cured at one pass. Ink B2 gave a harder surface with better marresistance than Ink A2. Mar resistance was evaluated by running a woodenstick along the film surface while applying pressure, and the marresistance is qualitatively evaluated by the severity of the mark leftby the stick.

EXAMPLE 3

Ink C (comparative) was prepared by combining with mixing: 20 partsMillbase A, 30 parts Oligomer B, 33 parts THFFA, 30 parts IBOA, 30 partsEEEA, 20 parts NVC, 10 parts HDDA, 4 parts TINUVIN 292, 1.8 partsSTABAXOL I, 0.2 parts IRGANOX 1035, 12 parts IRGACURE 819, 4 partsIRGACURE 651, 4 parts IRGACURE 369 and 2 parts IPTX

Ink D was prepared by combining with mixing: 18 parts Ink C and 2 partsethyl acetate (surface tension was 23.1 dyne/cm at 25° C.). Ink D had asolvent content of 10 weight percent.

Surface tension and viscosity of the two inks are shown in Table 2.

TABLE 2 Property Ink C (comparative) Ink D Viscosity (cP) 17.5 8.8Surface tension (dynes/cm) 34.1 32.0

The inks were printed on an x-y positionable platen using an XAARXJ128-360 printhead at 317×285 dpi resolution solid fill image on 3540Cpolyolefin film, 180-10 vinyl film and diamond grade retroreflectivefilm. Printed films were cured as described in Example 1. Adhesion, dotgain, and image quality (wetting) were evaluated and the results areshown below in Table 3.

TABLE 3 Ink C Ink C Ink C Ink D Ink D Dot Wet- Ink D Dot Wet- SubstrateAdhesion diameter ting Adhesion diameter ting 3540C 100% 62 3 100% 85 3film microns microns 180-10 100% 98 3 100% 123 2 vinyl film micronsmicrons Diamond  90% 150 1 100% 185 0 Grade microns microns

The results indicate that samples containing limited amounts of solventshow improved wetting and image quality in general, and better flow ofthe ink dots. Added solvent improves adhesion to diamond grade film.

EXAMPLE 4

This example describes the preparation of a magenta, UV curable inks.

A magenta millbase (Millbase B) was prepared by milling 33 partsRT-343-D magenta pigment, 11.55 parts SOLSPERSE 32000, and 55.45 partsTHFFA for 90 minutes using a Netzsch Mini-Zeta bead mill with 0.5 mmzirconia media.

Ink E was prepared by combining with mixing: 20 parts Millbase B, 4parts SR368, 5 parts PRO-4303, 5 parts EBECRYL 284, 1 part THFFA, 9parts EEEA, 6 parts IBOA, 24.5 parts IOA, 5 parts HDDA, 5 parts NVC, 2parts TINUVIN 292, 0.9 parts STABAXOL I, 6 parts IRGACURE 819, 3 partsIRGACURE 651, 2.5 parts IRGACURE 369 and 1 part IPTX.

Ink F was prepared by combining with mixing 18 parts Ink E and 2 partsethyl ACETATE. The solvent content of Ink F was 10 percent by weight.

Ink G was prepared by combining with mixing 19.99 parts Ink E and 0.01parts SF96-100 silicone flow agent.

Surface tension and contact angle of Inks E, F and G are shown in Table4.

TABLE 4 Contact angle with Contact angle with Surface tension 180-10vinyl film 3540C film (dynes/cm) (degrees) (degrees) Ink E 30.8 11.117.7 Ink F 29.2 9.6 15.7 Ink G 23.1 9.3 12.0

Adding 10% solvent resulted in a small change in surface tension, butsignificant reduction in contact angle, while adding flow agentdecreased the contact angle, but also resulted in too large decrease insurface tension, which is not desirable since piezo inks with surfacetension below about 26 dynes/cm result in nozzle plate flooding duringjetting from some printheads, leading to reduced ink reliability.Reduced contact angle allows increased dot gain and improved imagequality.

EXAMPLE 5

A black millbase (Millbase C) was prepared by milling 25 parts LampblackLB-1011 pigment, 5 parts Solsperse 32000 and 70 parts THFFA for 45minutes using a Netzsch Mini-Zeta bead mill with 0.5 mm zirconia media.

Ink H was prepared by combining with mixing: 10 parts Millbase C, 5parts SR368, 5 parts PRO-4303, 10 parts EBECRYL 284, 2 parts THFFA, 13.1parts EEEA, 7 parts IBOA, 23 parts IOA, 5 parts HDDA, 5 parts NVC, 2parts TINUVIN 292, 0.9 parts STABAXOL I, 5 parts IRGACURE 819, 3 partsIRGACURE 651, 3 parts IRGACURE 369 and 1 part IPTX.

Ink I was prepared by combining with mixing 41.2 parts Ink H, 5 parts ofethyl acetate and 3.8 parts of EBECRYL 284.

Ink J was prepared by combining with mixing 19.99 parts ink H and 0.01parts SF96-100 silicone flow agent.

Table 5 shows the surface tension and viscosity of the three inks.

TABLE 5 Surface tension Viscosity (dynes/cm) (centipoise) Ink H 30.816.6 Ink I 29.4 16.1 Ink J 23.4 16.5

Inks H, I, and J were jetted onto Diamond Grade film in a solid blockpattern using a XAAR XJ128-200 printhead at 317×295 dpi resolution. Theywere cured in air using a Fusion UV Systems UV processor with mediumpressure mercury lamp at 240 mJ/cm² exposure. Cure quality was measuredby rubbing the film with cotton tip applicator and mar resistance wasmeasured by rubbing the film with a wooden applicator. Qualitatively,cure and mar were evaluated on a scale from 1 to 5 where 1 indicatespoor quality, and 5 best quality. Results are shown in Table 6.

TABLE 6 Cure Rating Mar Resistance Rating Ink H 4 1 Ink I 4.5 4 Ink J 41

EXAMPLE 6

A cyan millbase (Millbase D) was prepared by milling 29.7 parts 249-1284Cyan 15:3 Pigment, 3.3 parts SOLSPERSE 5000, 13.2 parts SOLSPERSE 32000,and 53.8 parts THFFA for 45 minutes using a Netzsch Mini-Zeta bead millwith 0.5 mm zirconia media.

A series of cyan inks were prepared using Millbase D using the procedureof Example 1, but using formulation amounts as indicated in Table 7. InkK is a comparative example.

TABLE 7 Component/ Property Ink K Ink L Ink M Ink N Ink O Ink P Ink QInk R Ink S Ink T MILLBASE D 38 9.55 9.51 9.51 9.51 9.5 9.53 9.5 9.559.51 OLIGOMER B 52.35 13.03 13.04 13 13 13 13.01 17.05 20 25.09 THFFA 6611.52 11.52 11.5 11.53 11.5 11.51 9.5 9.1 5.1 EEEA 60.1 15 15.01 15.0111.01 11.05 11.06 10 7.99 6 IBOA 60.05 15 15 15.04 13.99 13.99 14 10.029 6 IOA 8 NVC 40.01 10.04 10 10.01 10.11 10 10 10 8 8.05 HDDA 20 5.015.02 5.01 5.01 5 5 5 4 4 TINUVIN 292 8.01 2.01 2.01 2 2.01 2 2.02 2.011.61 1.6 STABAXOL I 3.61 0.9 0.91 0.9 0.93 0.9 0.91 0.9 0.9 0.9 IRGANOX1035 0.42 0.12 0.1 0.1 0.12 0.1 0.1 0.11 0.1 0.1 IRGACURE 819 24.02 6.016 6.01 6 6.01 6 6.01 4.81 4.8 IRGACURE 651 8 2.01 2.01 2 2 2 2 2.01 1.611.6 IRGACURE 369 8.02 2.01 1 1.01 2 2.01 2.02 2 1.6 1.6 IPTX 4.03 1 1.021 1 1 1 1.01 0.8 0.8 EXXATE 800 5 10 EXXATE 700 5.01 10.01 EXXATE 600 510 15 20 25.01 Viscosity (cP) 14.7 14.18 14.09 14.09 11.38 13.38 12.9114.55 13.1 15.46 Reflective 2.1 2.15 2.13 2.13 2.16 2.14 2.23 2.17 2.182.18 Optical Density Flash ˜208 188 201 192 172 192 184 159 152 146Point (° C.) Surface 32.5 31.7 32.5 32.2 31.3 32 32.1 30.8 30.3 30Tension (Dyne/cm2)

Other embodiments of this invention will be apparent to those skilled inthe art upon consideration of this specification or from practice of theinvention disclosed herein. Various omissions, modifications, andchanges to the principles and embodiments described herein may be madeby one skilled in the art without departing from the true scope andspirit of the invention which is indicated by the following claims.

What is claimed is:
 1. A method of making an ink jettable fluidcomposition, comprising the steps of: (a) selecting a solvent componentto incorporate into the composition, wherein the solvent componentcomprises solvent having a surface tension and wherein said solvent isselected for incorporation into the composition from informationcomprising a solvent characteristic indicative of the solvent surfacetension; and (b) incorporating from about 1 to about 15 weight percentof the solvent into a composition comprising said solvent, one or moreoligo/resins, and a radiation curable, reactive diluent having a surfacetension, wherein the surface tension of the solvent is no more thanabout the surface tension of the radiation curable reactive diluent. 2.The method of claim 1, wherein the surface tension of the solvent isless than about 30 dynes/cm.
 3. The method of claim 1, wherein thesurface tension of the solvent is at least 2 dynes/cm less than thesurface tension of the radiation curable reactive diluent.
 4. The methodof claim 1, wherein the solvent is nonpolar.
 5. The method of claim 1,wherein the composition is substantially nonconductive.
 6. The method ofclaim 1, wherein the composition is at least substantially free of flowcontrol agents comprising silicone and/or fluorinated moieties.
 7. Themethod of claim 1, wherein the solvent is an acetate ester.
 8. Themethod of claim 1, wherein the solvent has a flash point of at least 50°C.
 9. The method of claim 1, wherein the composition comprises 1 to 10weight percent of the solvent.
 10. The method of claim 1, wherein thesolvent is an ester comprising a branched aliphatic moiety including 4to 20 carbon atoms.
 11. The method of claim 10, wherein the branchedaliphatic moiety is an isoalkyl moiety.
 12. The method of claim 1,wherein the solvent is at least substantially free of radiation curablemoieties.